Fabrication and performance of an advanced ceramic tool material

An advanced Al2O3-based ceramic tool material with carbon additive has been fabricated with hot pressing technique. Microstructures are analyzed with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Experiments show that this kind of ceramic tool material can achieve a fracture toughness of 5.89 MPa m1/2 which is approximately 20% higher than that of the corresponding ceramic material containing no carbon additive, while the hardness and the flexural strength do not decrease much. It is found that microcracking, crack deflection, crack branching and crack bridging may contribute dominantly to the increase in the fracture toughness of the carbon containing Al2O3/TiC ceramic tool material. Therefore, it can get higher fracture resistance while remaining good wear resistance in continuous and interrupted machining of hardened carbon steel. Under various face milling conditions, the increment of the fracture resistance of the carbon toughened ceramic tool material ranges from 17.5 to 30.2%. Wear mechanisms are mainly adhesion wear and abrasive wear, and thermal shock induced crack is one of the main reasons for the ceramic tool fracture when machining at high speed.